52100 processing

[Don Carlos Andrade]

Just curious what you-all have to say about Forging and heat treating 52100. What is the best source for information on working it with a very simple shop set-up?

I have read the Fowler book many years ago and have the impression that you need to have a digital oven to do some of the processing.

I have also talked to some friends in Brazil that use this steel all the time and say they just treat it like any other high carbon tool steel.

One thing I have heard is that you need to be very careful not to overheat it. What constitutes "overheating" beyond the obvious.

Thanks for your feedback.

-DON

 

[BobH]

Don,
I'll take a stab, before some one who really knows jumps in.
1625°. To tell if you are close the scale flakes on your anvil should be very small to dust. Keep a pail of quench at your forge to quench the tip so it doesn't overheat while the rest of the blade catches up.
Your kitchen oven will work fine. Just get an oven thermometer to make sure the temps are accurate.
I've only made a couple of blades out of 52100, but I followed Ed's "KNIFE TALK", and they turned out fine.
Bob

 

[Don Carlos Andrade]

Thanks Bob,
I'm feeling like from what I have been hearing that there is no need to have a digital oven to do some of the special thermal-cycling that I read about years ago.

Looking forward to hearing what others have to say.

-DON

 

[BobH]

The thermal cycling I did in the forge. Tempering in the kitchen oven. The edge flexed beautifully over a brass rod.
I hope someone elese jumps in here.
Bob

 

[Doug Lester]

I use 52100 and here are some pointers that I picked up. Like any other hypereutectic steel, you don't want to heat the steel above the upper critical point. My forge will run in the mid 1600 degrees F (that looks like around 950 C.) and I soak it for five minutes at a dark red. I then austemper it in an oil bath at 450 degrees F. (about 225 degrees C.) for four hours. The oil temperature in the bath is just a little under the Ms point, probably around M25%, which gives a little added hardness to the blade. The four hour soak is just to make sure that the rest of the austinite is converted to bainite. The ITT diagram shows that the bainite finish line is probably more at the 1 hour mark but the diagram shows that the data in that area is a little impresice and the extra time won't hurt. Hopefully, I really don't have a way to have the blades tested, I end up with 25% tempered martensite and 75% lower bainite. I may end up getting a Rockwell hardness tester but right now all I can do is cut soft steel wire and the edge seems to hold up well.

One of these days I may find a way to hold the oil, or molten salt, bath at about 500-525 degrees F. (a little over 250 degrees C.) so that I can quench to 450 in oil then up quench to the higher temperature and hold the steel in the austempering bath for 1-1 1/2 hours.

If the blade is held at or just above 480 degrees F. (maybe around 240 degrees C.) you can go for 100% bainite for a hardness of around 58 HRC.

As far as needing a heat treating oven for hardening and tempering steel, that would probably be helpful with any steel to get the best performanc and mandatory for the high alloy steels. Some of the higher alloy steels also require a higher temperature to temper than a kitchen or toaster oven can obtain. A heat treating oven is necessary if you are tying for secondary hardening with a higher alloy steel but I don't agree with Ed Fowler that you need that kind of heat regulation to heat treat steels like 5160 or 52100, his favorites.

Doug